When you first startup all startup items are then fully loaded. Once you come back from standby you lose some of those processes since they were unloaded once the system goes into standby mode. You would then have to see a full system restart to see all items loaded up again.
As expected any newer version of Windows will use more memory as memory capacity on boards also sees an increase. The hardwares are actually moving faster in that sense with boards now seeing 8gb and 16gb capacities while lacking the chipsets needed.
XP was a large jump memory wise over 98 when you look back through the older versions. 512mb of memory was large then. 98 could run on 16mb. Systems then came with 64 or 128mb. XP machines would later come with 128 or 256mb installed.
Newer OS with more and larger features plus whatever new startups you add often simply require an increase in the memory on a system. 2gb is a good standard for a Vista machine while 1gb sufficed often for XP. For CAD and memory hungry large programs then you consider the increase to something like 4gb knowing the loss of some for hardware mapping is to be expected.
Even the 64bit editions see problems at times when going to install Windows there with 4gb installed. The MS solution for that is first removing 2gb until Windows is up and running properly. Then you simply toss the other 2gb back in.